Primary nonadherence to medications in an integrated healthcare setting

To measure primary nonadherence (PNA) rates for 10 therapeutic drug groups and identify factors associated with PNA to chronic and acute medications.

Retrospective cohort study.

New prescriptions written in an integrated healthcare system for study drugs were identified between December 1, 2009, and February 28, 2010. PNA was defined as the failure to fill a prescription within 14 days of when it was written. PNA rates were calculated by drug group and descriptive statistics were performed. Multivariable logistic regression was used to identify significant patient, provider, and prescription characteristics associated with PNA. Results were stratified by acute versus chronic treatment.

A total of 569,095 new prescriptions were written during the 3-month period. Across all drug groups, the PNA rate was 9.8%. PNA rates for individual drug groups varied and were highest for osteoporosis medications (22.4%) and antihyperlipidemics (22.3%). Patients who filled at least 1 prescription in the prior year (odds ratio [OR], 95% confidence interval [CI] for acute = 0.06 [0.06-0.07], for chronic = 0.11 [0.10-0.12]) or had a prescription for a symptomatic disease (OR = 0.51 [0.48-0.53]) were more likely to fill their prescription. Patients were more likely to be primary nonadherent if they were black (OR acute = 1.30 [1.25-1.36], chronic = 1.26 [1.18-1.33]) or treatment-naive to therapy (OR acute = 2.52 [2.36-2.7], chronic=1.07 [1.03-1.12]).

Overall PNA was 9.8% but individual PNA rates varied by therapeutic drug group. Factors of PNA were mostly consistent across drug groups, but some depended on whether the treatment was acute or chronic.